Southbound Interstate 79 has reopened after a tractor-trailer overturned at the bridge over Route 51 (mile marker 65) in Robinson Township.

State police said the tractor-trailer was traveling south on I-79 when the driver lost control at the exit for Route 51 about 9:15 a.m. Thursday and the vehicle slid up to 500 feet before it rolled on its side and came to rest next to a guiderail near the edge of the overpass.

"It's called Celite," said Robinson Township Fire Chief Kenny Kiskow. "(It's) used in water filtration systems. It's an irritant but non-hazardous."

It took more than 5 hours for crews to get the trailer upright. Fire officials said the powder could only be cleaned up with a vacuum because any contact with water could cause a chemical fire.

"It's a long process. It's a powdery material on a windy day. It just doesn't want to cooperate, said Kiskow.

As traffic backed up on I-79 due to the overturned tractor-trailer, another crash was reported near mile marker 67.1.

State police said a 63-year-old driver of a Mercedes Benz SUV didn't stop and rear-ended an Acura RDX, police said. The 21-year-old driver of the Acura suffered severe injuries and was taken by ambulance to Allegheny General Hospital, police said. The driver of the Mercedes was not injured.

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